In a projector that includes a liquid crystal panel, in order to reduce the amount of loss of light (normally unpolarized light) incident from the light source upon the liquid crystal panel, and in order to utilize this light with good efficiency, there is included an optical element for aligning the direction of polarization of the incident light into one direction before emitting it. The conventional optical element disclosed in Patent Document #1 is a plate shaped light polarization element in which a polarization splitting layer is provided upon one surface of a transparent parallel flat plate, and, when a ray bundle that has passed through a cylindrical lens is incident thereupon at an angle of 45°, this element separates the incident light into a reflected component that is polarized in one direction, and a transmitted component that is polarized in the other direction. The reflected light component is emitted just as it is at an angle of 90° with respect to the direction of incidence, while the transmitted light component is internally reflected by the opposite side of the transparent parallel flat plate that converts its direction of polarization, and is then emitted in parallel to the reflected light component. According to this optical element, the directions of polarization of the emitted light components are aligned to one another, so that the efficiency of utilization of the light is enhanced (refer to Patent Document 1).
Patent Document 1: Japanese Laid-Open Patent Publication No. H5-107505